Scn1ba_tv1 staining appears in the poc and TeO as well as in the rostral hypothalamus (Hr), but is absent in the subcommisural organ (SCO). subunit protein expression was examined in greater detail in the retina and optic nerve (Fig. Scn1ba_tv1 and Scn1ba_tv2 are identical except for their C-terminal domains. The C-terminus of Scn1ba_tv1 contains a tyrosine residue similar to that found to be critical for ankyrin association and Na+ channel modulation in mammalian 1. In contrast, Scn1ba_tv2 contains a unique, species-specific C-terminal domain that does not contain a tyrosine. Immunohistochemical analysis shows that, while the expression patterns of Scn1ba_tv1 and Scn1ba_tv2 overlap in some areas of the brain, retina, spinal cord, and skeletal muscle, only Scn1ba_tv1 is expressed in optic nerve where its staining pattern suggests nodal expression. Both em scn1ba /em splice forms modulate Na+ currents expressed by zebrafish em scn8aa /em , resulting in shifts in channel gating mode, increased current amplitude, negative shifts in the voltage dependence of current activation and inactivation, and increases in the rate of recovery from inactivation, similar to the function of mammalian 1 subunits. In contrast to mammalian 1, however, neither zebrafish subunit produces a complete shift to the fast gating mode and neither subunit produces complete channel inactivation or recovery from inactivation. Conclusion These data add to our understanding of structure-function relationships in Na+ channel 1 subunits and establish zebrafish as an ideal system in which to determine the contribution of em scn1ba /em to electrical excitability em in vivo /em . Background Voltage gated Na+ channel 1 ( em Scn1b /em ) subunits are multi-functional proteins that participate in inter- and intra-cellular communication on multiple time scales via modulation of electrical signal transduction and cell adhesion [1,2]. 1 subunits modulate Na+ currents [3], regulate the level of Na+ channel cell surface expression [4], and participate in cell adhesive interactions that lead to changes in cell migration [5], cellular aggregation [6], cytoskeletal recruitment [7,8], and/or neurite outgrowth em in vitro /em [9]. Mice Rabbit Polyclonal to OR2M7 lacking 1 Zileuton subunits exhibit seizure activity, ataxia, slowed action potential conduction, decreased numbers of mature nodes of Ranvier in myelinated axons, alterations in nodal architecture, and differences in Na+ channel subunit localization [10]. Thus, 1 subunits play critical roles in electrical excitability em in vivo /em . However, while em Scn1b /em null mice are interesting, their early death at postnatal day 19 and complex phenotype make them a challenging model system. As a first step toward development of an alternative model system in which to study the physiological roles of Na+ channel 1 subunits em in vivo /em we chose em D. rerio /em . This is an attractive model system with a number of advantages over mice, including the production of large numbers of embryos per single pair mating, external fertilization with transparent larvae allowing for genetic manipulation Zileuton from the one cell stage, and rapid development [11]. Embryos contain most of their adult structures by 48 hours post-fertilization (hpf) Zileuton and the majority of external and internal organs Zileuton reach maturity by 5 days post-fertilization (dpf). Other commonly studied genetic model systems such as em Drosophila /em or em C. elegans /em were not appropriate for an em in vivo /em investigation of Na+ channel subunits. There are no obvious candidates for voltage-gated Na+ channel gene orthologs in the genome of em C. elegans /em [12]. While the em Drosophila /em genome encodes two Na+ channel subunit genes, orthologs of Na+ channel subunits appear to be lacking, suggesting that these subunits arose in evolution after the appearance of invertebrates [13]. Na+ channel subunit genes have been extensively studied in zebrafish, where eight different em SCNA /em orthologs have been identified [14,15]. This is the first description of the structure and localization of a zebrafish Na+ channel subunit ortholog, although sequences of em SCN2B /em , em SCN3B /em , and em SCN4B /em orthologs have recently been reported in GenBank. In the present study we report the cloning.